第31章

By this means, the author obtained impressions instantaneously in the sunshine, and in five to ten seconds in a moderate light;and he hopes to be able to take moving objects. It can be applied by exposing the prepared plate over a surface of water, to which a few drops of ammonia have been added (sufficient to make it smell of ammonia);or the vapor can be introduced into the camera during the action.

In fact, the presence of ammonia, in the operating-room, appears to have a good effect, as it also neutralizes the vapors of iodine and bromine that may be floating about, and which are so detrimental to the influences of light upon the plate."GALVANIZING THE DAGUERREOTYPE PLATE.

In consideration of the importance of galvanized plates, I shall endeavor to give as plain and concise a manner of manipulation as possible.

For some time it was a question among the operators generally, as to the beneficial result of electrotyping, the Daguerreotype plate, but for a few years past our first operators have found it a fact, that a well electro-silvered surface is the best for producing a portrait by the Daguerreotype.

From my own experiments, I have found that a plate, by being galvanized, can be rendered more sensitive to the operation of the light in proportion of one to five, viz.: if a plate as furnished by the market, be cleaned, polished, coated and exposed in the camera, if the required time to freely develop an impression be ten seconds, a similar plate prepared in like manner and galvanized, will produce an equally well-defined image in eight seconds.

In connection with this subject, there is one fact worthy of notice;a plate with a very heavy coating of pure silver, will not produce an equally developed image, as a plate with a thinner coating, hence the thin coating, providing it entirely covers the surface, is the best, and is the one most to be desired. The experiment is plain and simple.

Let the slate receive a heavy or thick coating by the electrotype, then polish, coat, expose in the usual manner, and the result will be a flat, ashy, indistinct impression; when, on the other hand, the thin coating will produce a bright, clear and distinct image, with all the details delineated.

The style of battery best for the purpose has been, and now is, a question of dispute among operators; some preferring the Daniell battery to Smee's. Some claim the superiority of the first from its uniformity of action; others, of the latter, for its strength.

I consider either good, and for the inexperienced would prefer the Daniell.

This is more simple in its construction, while it has certainty in action.

The more skillful electrotyper would prefer Smee's, and this is the one most generally in use. I would remark that the plan of galvanizing plates should be followed by every operator, and when once thoroughly tested, no one will abandon it.

SILVERING SOLUTION.

To any desired quantity of chloride of silver in water add, little by little, cyanide of potassium, shaking well at each addition, until all the cyanide is dissolved. Continue this operation, and add the cyanide, until all the precipitate is taken up and held in solution.

This solution is now ready for the plate-cup. Enough water may be added to cover any sized plate when held perpendicular in the cup.

The strength of the solution may be kept up by occasionally adding the chloride of silver and cyanide of potassium.

There should alway be a very little excess of the cyanide.

The plate should be well cleaned and buffed, and the solution well stirred before it is immersed. Care should be observed to keep the solution clean, and allow no particle of dust to come in contact with the surface of the plate.

The plate is now to be attached to the pole of the battery.

After remaining a short time, it assumes a blue color; take it out, rinse freely with pure water, then dry with a spirit lamp, and it is ready for buffing. Buff and coat in the usual manner.

Some operators are in the practice of immersing the plate in the solution and buffing twice. This additional silvering is no improvement wherever there has been a proper first coating.

Sometimes the operator is troubled with streaks or scum on the plate.

This may arise from three causes, all of which experience must teach the experimenter to avoid; first, too great an excess of cyanide in the solution; second, a lack of silver; third, the current too strong.

Another annoyance arises from the solution being dirty and the dirt collecting on the surface. When this is the case, the dirt is sure to come in contact with the surface of the plate as it is plunged into the solution, and the result is a scum that it is difficult to dispose of.

This can be prevented only by frequent filtering. One thing should always be borne in mind in electrotyping Daguerreotype plates--that in order to secure a perfectly coated surface, the plate should be perfectly cleaned.

In this point, many who have tried the electrotype process have failed, attributing their ill success to other than the proper cause.

DAGUERREOTYPES WITHOUT MERCURY.

The following process possesses some interest, and is worthy a trial from operators. M. Natterer, of Vienna, discovered a process for obtaining proofs on iodized plates with the chloride of sulphur, without the use of mercury.

A plate of silver is iodized in the usual manner, and then placed on the top of a vessel six or eight inches high, having at the bottom, in a small cup, a few drops of chloride of sulphur;it should remain exposed to the action of the vapor until the sombre yellow color is changed to a red, after which it is brought to a focus m the camera, where it is exposed to the light in the camera, for about the time necessary to produce an ordinary daguerreotype. The plate is then taken out and examined in the camera by the light of a candle.